1. Field of Invention
The present invention relates to electrical connections internal to hermetic compressor assemblies, particularly with regard to connectors designed to protect against electrical arcing across carbon deposits which may be formed within the compressor assembly, and methods of providing arc prevention within hermetic compressor assemblies.
2. Description of the Related Art
The terminal assembly extends through the sealed shell, or housing, of a hermetic compressor and includes a terminal body and a plurality of conductor pins which extend through apertures located in the terminal body. The terminal body is usually welded or brazed into an aperture provided in the compressor assembly housing. The conductor pins are secured within these apertures and are electrically insulated from the terminal body and the housing by fused glass insulators. An electric motor having a stator and a rotor is located within the housing, with the rotor being operatively coupled to a compression mechanism. The interior ends of the conductor pins are connected to lead wires which are connected to the windings of the motor stator. The exterior ends of the conductor pins are selectively connected to a source of electrical power. Thus, the motor is energized by the external power source through the terminal body, the lead wires, and the electrical connections therebetween. The electrical connections typically include an electrical connector attached to each lead wire and engaged with a corresponding conductor pin. A plurality of connectors and portions of their respective lead wires are normally assembled into, and housed by, a cluster block comprising the cluster block assembly.
The cluster block is dielectric, usually composed of an injection-molded plastic, and facilitates quick assembly of the lead wires to the terminal assembly. The cluster block also insulates the electrical connectors therein from each other, and from the terminal assembly and compressor housing, to a substantial degree. Usually, the interior of the cluster block is formed with a plurality of separated passages, each passage receiving one lead wire, and a plurality of recesses for receiving each of the connectors attached to the ends of the lead wires. Passages leading to these connectors are provided through the cluster block with the conductor pins of the terminal assembly extending therethrough.
During compressor operation, carbon or other conductive deposits from the motor may collect on the interior surfaces of the housing and perhaps the terminal assembly. These deposits may provide a conductive path between elements having different electrical potentials, thereby causing a short circuit or arc to develop along the conductive path. Such arcing results in the resistive heating of the deposits along the conductive path, in turn heating the elements on which the deposits collect. Such heating is known to sometimes cause the fused glass insulators surrounding the conductor pins to melt, thereby causing the compressor housing to leak pressurized gas at the terminal assembly.
Prior hermetic compressor assemblies often include some means for impeding such arcing. These means usually include a design which is intended to prevent the conductive deposits from collecting on the interior surface of the terminal assembly and its glass insulators. These means include electrical connector or cluster block assemblies through which the lead wires are attached to the interior ends of the conductor pins, and which, when assembled to the terminal assembly, substantially cover the conductor pins and lead wires. However, some prior cluster block assemblies may not completely preclude the formation of a conductive path between the lead wire ends and/or electrical connectors within the cluster block, and the terminal body or compressor housing.
Some of these previous cluster block assemblies include sealing features which help prevent the conductive deposits from entering the interior of the terminal assembly past its interface with the cluster block. One such cluster block assembly includes a cylindrical exterior wall portion that sealingly engages the cylindrical interior surface of the terminal body, as by an interference fit; the cylindrical interface may also include additional sealing means such as an O-ring. A problem associated with prior cluster block assemblies which sealably engage the terminal assembly in this manner is that they may be improperly installed, the proper seating of the block relative to the terminal assembly being hindered by the interference fit between the terminal body and the cluster block, or the O-ring therebetween.
Other cluster block assemblies include a layer of epoxy, or another elastomeric material, to surround the conductor pins and coat the insulators, or the use of sleeves to surround the conductor pins which are then filled with an epoxy or other material. A problem with such cluster block assemblies is that the conductor pins and the interior of the housing may not be completely sealed from each other to prevent the collection of the conductive materials on the terminal assembly, thereby allowing the previously mentioned arcing to occur. Another problem is that this sealing method requires additional steps in the assembly process, such as placing the layers on the respective parts prior to completion of the assembly, or that the process would require additional time for the seals to cure before completion of the assembly.
A cluster block assembly that is able to be assembled with little, if any additional steps, able to protect against the collection of conductive materials between elements at different electrical potentials, thereby prevent the formation of arcs, and able to avoid the above-mentioned shortcomings of previous cluster block assemblies, is highly desirable.